A turbojet engine can be mounted at various locations of an aircraft, through a fixing strut belonging to said aircraft's structure. For instance, the turbojet engine can be suspended, through said fixing strut, to the aircraft wing intrados, or attached laterally to the fuselage, or else mounted, at the rear of the aircraft, on the rear vertical empennage. The function of fastening structures connecting the fixing strut to the turbojet engine is to ensure the transmission of mechanical force between the turbojet engine and the aircraft structure.
The force transmitted to the aircraft structure through the fastening structures are mainly thrust loads from the turbojet engine, extending parallel to the turbojet engine axis, lateral forces mainly due to wind gusts to which the turbojet engine and the aircraft are generally submitted, and vertical forces from said turbojet engine mass. The fastening structures should also absorb turbojet engine distortions, i.e., from dimensional variations due to thermal dilations or contractions during various aircraft flight phases.
Generally, fastening structure for fastening the turbojet engine to the aircraft fixing strut includes a front attachment device and a rear attachment device.
Fastening structures commonly used include the turbojet engine central cowl attached to the fixing strut using a front attachment device and a rear attachment device. In that case, the front attachment device absorbs the turbojet engine thrust loads as well as the lateral and vertical forces. The rear attachment device absorbs lateral and vertical forces.
Other fastening structures include a front attachment device, arranged between the fixing strut and the fan cowl, which absorbs lateral and vertical forces, and a rear attachment device, arranged between the fixing strut and the central cowl, which absorbs thrust loads, lateral forces and vertical forces. Thrust loads are then absorbed through two long rods, connecting the rear attachment device to a front part of the central cowl.
As a result of the turbojet engine thrust loads, and more specifically from said thrust load absorption by the attachment device and the fixing strut, the turbojet engine is submitted to significant bending, which tends to decrease the turbojet engine life span.
The present invention provides a device for fastening a turbojet engine to a fixing strut adapted to absorb the turbojet engine thrust loads and to transmit them to the fixing strut, without subjecting the turbojet engine to significant bending forces.
In that regards, the invention includes a front attachment mechanism, connecting the fixing strut to the turbojet engine fan cowl, forming a thrust load absorption vector resulting from different attachment points between aforesaid front attachment mechanism and the turbojet engine, which is directly coincident with the turbojet engine axis. The front attachment mechanism according to the invention includes an intermediate part, positioned under a main part of the turbojet engine front attachment mechanism. The intermediate part is linked to the main part by a first attachment system, which convergence point is located on the turbojet engine axis. The intermediate part is also connected to the turbojet engine through a second attachment system, which convergence point is also located on the engine axis, but upstream from the first attachment system convergence point. The front attachment mechanism according to the invention behaves as if the engine thrust was transiting between both attachment system convergence points of said front attachment mechanism, i.e. following the turbojet engine axis, and therefore without generating the slightest bending of said turbojet engine, the torque being naturally absorbed completely by the fixing strut.
The second attachment system, connecting the intermediate part to the turbojet engine, includes, for example, a rod system in the front and anti-torque controls in the rear. Front and rear as used herein are designated in relation to the moving direction of an aircraft having such turbojet engine. The intermediate part according to the invention, since the anti-torque controls and rod systems are connecting it, on the one hand, to the turbojet engine and, on the other hand, to the main part of the front attachment mechanism, has particular kinematics enabling a thrust load transfer along the axis of the turbojet engine. The geometry of the front attachment mechanism according to the invention is designed so that the resulting force from the various fixing points is coincident with the turbojet engine axis, so that said turbojet engine is not submitted to any bending force.
Therefore, the invention provides a front attachment device for fastening a turbojet engine to an aircraft fixing strut adapted to absorb said turbojet engine thrust loads, wherein the front attachment device includes a top bracket, a lower bracket, primary fixing points connecting said top bracket to lower bracket, and secondary fixing points connecting said lower bracket to said turbojet engine, the absorbing thrust loads vector which results, on the one hand, from the convergence point of the primary vectors passing through the primary fixing points, and, on the other hand, from the convergence point of the secondary vectors passing through the secondary fixing points, and which transmits the turbojet engine thrust loads to the fixing strut, extends along the axis of the turbojet engine.
Fastening point used herein is defined as any punctual attachment mechanism, enabling connection of one element to another through a specific point.